Year	US Dollars
1960	4.02773
1961	3.63836
1962	2.27927
1963	2.34893
1964	2.62024
1965	2.911
1966	2.1076
1967	2.99756
1968	3.20596
1969	2.54319
1970	2.65985
1971	2.13612
1972	3.316
1973	3.13563
1974	3.69851
1975	4.90446
1976	7.98407
1977	6.58696
1978	4.88881
1979	6.1572
1980	6.08968
1981	5.45453
1982	6.03223
1983	7.6381
1984	6.33388
1985	9.64227
1986	15.0933
1987	28.60745
1988	24.64299
1989	27.08382
1990	20.54228
1991	20.56403
1992	20.78676
1993	22.35303
1994	19.52972
1995	19.9625
1996	17.35228
1997	23.75708
1998	20.84786
1999	24.83406
2000	22.49399
2001	19.1348
2002	20.84706
2003	20.88627
2004	18.41255
2005	20.81201
2006	37.89128
2007	34.50541
2008	39.26692
2009	27.18249
2010	28.19557
2011	24.34801
2012	20.62584
2013	33.00988
2014	18.28265
2015	26.41992
2016	16.77124
2017	22.81348
2018	24.43392
2019	23.38288
2020	28.04607
2021	29.88122